ISSN: 1693-6930, accredited First Grade by Kemenristekdikti, Decree No: 21/E/KPT/2018
DOI: 10.12928/TELKOMNIKA.v18i2.15857 1072
Physical security with power beacon assisted in half-duplex relaying networks
over Rayleigh fading channel: performance analysis
Phu Tran Tin1, Duy-Hung Ha2, Luu Gia Thien3, Tran Thanh Trang4
1Faculty of Electronics Technology, Industrial University of Ho Chi Minh City, Vietnam
2Wireless Communications Research Group, Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Vietnam
3Posts and Telecommunications Institute of Technology Ho Chi Minh City Campus, Vietnam
4National Key Laboratory of Digital Control and System Engineering, Vietnam
Article Info ABSTRACT
Article history:
Received Jul 24, 2019 Revised Nov 19, 2019 Accepted Dec 4, 2019
In this research, we proposed and investigated physical security with power beacon assisted in half-duplex relaying networks over a Rayleigh fading channel. In this model, the source (S) node communicates with the destination (D) node via the helping of the intermediate relay (R) node.
The D and R nodes harvest energy from the power beacon (PB) node in the presence of a passive eavesdropper (E) node. Then we derived the integral form of the system outage probability (OP) and closed form of the intercept probability (IP). The correctness of the analytical of the OP and IP is verified by the Monte Carlo simulation. The influence of the main system parameters on the OP and IP also is investigated. The research results indicated that the analytical results are the same as the simulation ones.
Keywords:
Energy harvesting (EH) Half-duplex (HD) Intercept probability (SP) Monte carlo simulation
Relaying network This is an open access article under the CC BY-SA license.
Corresponding Author:
Duy-Hung Ha,
Wireless Communications Research Group Faculty of Electrical and Electronics Engineering Ton Duc Thang University, Ho Chi Minh City, Vietnam.
Email: [email protected]
1. INTRODUCTION
Radiofrequency (RF) energy harvesting (EH) in the wireless communication network is become a novel solution for the communication network with battery-limited devices and has attracted massive attention in research and industrial directions. The communication network with the battery-limited devices or devices and wireless sensors, which are working in the dangerous conditions is the main inside human bodies object of RF EH wireless communication network application. This solution can be considered as the main one because of carrying both energy and information of the EF, to help the battery-limited devices to harvest energy for information transmission to the destination. This technic is called simultaneous wireless information and power transfer (SWIPT) [1-11]. Nowadays, the physical layer security (PLS) in EH communication cooperative relaying network is popularly studied with considerable interest. The first concept of PLS was proposed by authors in [12, 13]. In this paper, the author proposed the secret communication between the source and destination nodes with the presence of the eavesdropper channel.
Furthermore, the côperative jammer is used for secure the cooperative relaying network by degrading the eavesdropper’s channel is proposed and studied in [14, 15]. In this cooperative network, the jammer not
only is used to degrade the eavesdropper’s channel but also is helpful for increasing the EH process of the energy receiver in the cooperative relaying network. Moreover, a harvest-and-jam (HJ) protocol with multi-relay and multi-node in the cooperative relaying network was proposed in [16] to improve the secrecy rate of the energy harvesting and information transmission. Also, different secure relay beam-forming algorithms for SWIPT were discussed in [17-20].
In this research, we proposed and investigated physical security with power beacon assisted in half-duplex relaying networks over a Rayleigh fading channel. In this model, the source (S) node communicates with the destination (D) node via the helping of the intermediate relay (R) node. The D and R nodes harvest energy from the power beacon (PB) node in the presence of a passive Eavesdropper (E) node.
Then we derived the integral form of the system outage probability (OP) and closed form of the intercept probability (IP). The correctness of the analytical of the OP and IP is verified by the Monte Carlo simulation.
The influence of the main system parameters on the OP and IP also is investigated. The research results indicated that the analytical results are the same as the simulation ones.
2. SYSTEM MODEL
In Figure 1, the source (S) node communicates with the destination (D) node via the helping of the intermediate relay (R) node. The D and R nodes harvest energy from the power beacon (PB) node in the presence of a passive Eavesdropper (E) node. Figure 2 draws the energy harvesting (EH) and information processing (IT) of the model system. In this protocol, the transmission is divided into blocks of length T, which consists of three-time slots. In the first time slot αT (α is the time switching factor, 0<α<1), the S and R harvest energy from the PB node. In the remaining intervals time (1-α)T/2, the source S transfers the information to R, and R transfers information to D node [21-25].
Figure 1. System model Figure 2. Time switching protocol
2.1. Energy harvesting phase
In the first phase, the power beacon will supply the energy for both S and R nodes.
Hence, the harvested energy at the source and relay can be given as, respectively
𝐸𝑠= 𝜂𝑃𝐵𝛼𝑇|ℎ𝐵𝑆|2 (1)
𝐸𝑅= 𝜂𝑃𝐵𝛼𝑇|ℎ𝐵𝑅|2 (2)
where 0 < 𝜂 ≤ 1 is energy conversion efficiency, PB is the average transmitted power at the power beacon, and hBS, hBR are the channel gain of B-S link, B-R link, respectively. The average transmitted power at the source and relay nodes can be obtained from (1) and (2), respectively
𝑃𝑠= 𝐸𝑠
(1−𝛼)𝑇/2=𝜂𝑃𝐵𝛼𝑇|ℎ𝐵𝑆|2
(1−𝛼)𝑇/2 = 𝜅𝑃𝐵|ℎ𝐵𝑆|2 (3)
𝑃𝑅= 𝜅𝑃𝐵|ℎ𝐵𝑅|2 (4)
where =2𝜂𝛼
1−𝛼 .
2.2. Information transmission phase
In the second phase, the received signal at the relay can be rewritten as
𝑦𝑟=ℎ𝑆𝑅𝑥𝑠+ 𝑛𝑟 (5)
where hSR is the channel gain of S-R link, xs is the transmitted signal from source and nr is additive white Gaussian noise (AWGN) with variance N0. In the third phase, the received signal at the destination can be given by
𝑦𝑑=ℎ𝑅𝐷𝑥𝑟+ 𝑛𝑑 (6)
where hRD is the channel gain of R-D link, xr is the transmitted signal from relay and nd is (AWGN) with variance N0. Here, we consider amplify and forward (AF) mode at R. Hence, the amplifying factor can be given as
𝜒 =𝑥𝑟
𝑦𝑟= √𝑃 𝑃𝑅
𝑠|ℎ𝑆𝑅|2+𝑁0 (7)
substituting (7) into (6), we have
𝑦𝑑=ℎ𝑅𝐷𝜒𝑦𝑟=ℎ𝑅𝐷𝜒[ℎ𝑆𝑅𝑥𝑠+ 𝑛𝑟] + 𝑛𝑑=ℎ⏟ 𝑆𝑅ℎ𝑅𝐷𝜒𝑥𝑠
𝑠𝑖𝑔𝑛𝑎𝑙
+ℎ⏟ 𝑅𝐷𝜒𝑛𝑟+ 𝑛𝑑
𝑛𝑜𝑖𝑠𝑒
(8)
3. SYSTEM PERFORMANCE ANALYSIS
From (8), the end to end signal to noise ratio (SNR) of S-R-D link can be calculated as (9).
𝛾𝑆𝑅𝐷=𝛦{|𝑠𝑖𝑔𝑛𝑎𝑙|2}
𝛦{|𝑛𝑜𝑖𝑠𝑒|2} =|ℎ𝑆𝑅|2|ℎ𝑅𝐷|2𝜒2𝑃𝑠
|ℎ𝑅𝐷|2𝜒2𝑁0+𝑁0 =|ℎ𝑆𝑅|2|ℎ𝑅𝐷|2𝑃𝑠
|ℎ𝑅𝐷|2𝑁0+𝑁0 𝜒2
(9)
After doing some algebra and using the fact that N0<<PR, the (9) can be rewritten as (10).
𝛾𝑆𝑅𝐷= |ℎ𝑆𝑅|2|ℎ𝑅𝐷|2𝑃𝑠𝑃𝑅
𝑃𝑅|ℎ𝑅𝐷|2𝑁0+𝑁0𝑃𝑠|ℎ𝑆𝑅|2 (10)
Substituting (3) and (4) into (10), the SNR can be reformulated as (11).
𝛾𝑆𝑅𝐷=|ℎ𝑆𝑅|2|ℎ𝑅𝐷|2𝜅𝛹|ℎ𝐵𝑆|2|ℎ𝐵𝑅|2
|ℎ𝐵𝑅|2|ℎ𝑅𝐷|2+|ℎ𝐵𝑆|2|ℎ𝑆𝑅|2 =𝜅𝛹𝑋𝑌
𝑋+𝑌 (11)
Where =𝑃𝐵
𝑁0, 𝑋 = |ℎ𝐵𝑅|2|ℎ𝑅𝐷|2, 𝑌 = |ℎ𝐵𝑆|2|ℎ𝑆𝑅|2 . The received signal at the eavesdropper can be given by
𝑦𝐸=ℎ𝑅𝐸𝑥𝑟+ 𝑛𝐸 (12)
where hRE is the channel gain of R-E link and nE is AWGN with variance N0. The SNR at the eavesdropper can be expressed as
𝛾𝐸=|ℎ𝑅𝐸|2𝑃𝑅
𝑁0 (13)
substituting (4) into (13), we have:
𝛾𝐸= 𝜅𝛹|ℎ𝐵𝑅|2|ℎ𝑅𝐸|2= 𝜅𝛹𝑍 (14)
Where 𝑍 = |ℎ𝐵𝑅|2|ℎ𝑅𝐸|2
Lemma1. Please note that all channel are the Rayleigh fading channels, so the probability density function (PDF) of |ℎ𝑖|2 can be given by:
𝑓|ℎ𝑖|2(𝑥) = 𝜆𝑖𝑒−𝜆𝑖𝑥 (15)
where 𝑖 ∈ (𝑆𝑅, 𝑅𝐷, 𝐵𝑆, 𝐵𝑅, 𝑅𝐸). Moreover, the cumulative distribution function (CDF) of |ℎ𝑖|2 also can be obtained by
𝐹|ℎ𝑖|2(𝑥) = 1 − 𝑒−𝜆𝑖𝑥 (16)
where𝜆𝑖is the mean value of the exponential random variable |ℎ𝑖|2. Lemma 2. The CDF of 𝑋and Y can be computed as respectively
𝐹𝑋(𝑎) = ∫ 𝐹|ℎ𝑅𝐷|2( 𝑎
|ℎ𝐵𝑅|2||ℎ𝐵𝑅|2= 𝑥) 𝑓|ℎ𝐵𝑅|2(𝑥)𝑑𝑥
∞
0 (17)
𝐹𝑌(𝑏) = ∫ 𝐹|ℎ𝑆𝑅|2( 𝑏
|ℎ𝐵𝑆|2||ℎ𝐵𝑆|2= 𝑦) 𝑓|ℎ𝐵𝑆|2(𝑦)𝑑𝑦
∞
0 (18)
utilizing the result in [26], the CDF of X and Y can be shown as the below equation, respectively 𝐹𝑋(𝑎) = 1 − 2√𝜆𝑅𝐷𝜆𝐵𝑅𝑎𝐾1(2√𝜆𝑅𝐷𝜆𝐵𝑅𝑎) (19) 𝐹𝑌(𝑏) = 1 − 2√𝜆𝑆𝑅𝜆𝐵𝑆𝑏𝐾1(2√𝜆𝑆𝑅𝜆𝐵𝑆𝑏) (20) where 𝐾𝑣(•)is the modified Bessel function of the second kind and vth order. From (21) and (22), the PDF of X and Y can be calculated as, respectively after applying the formula
𝜕𝐾𝑛(𝑧)
𝜕𝑧 = −𝐾𝑛−1(𝑧) −𝑛
𝑧𝐾𝑛(𝑧) 𝑓𝑋(𝑎) =𝜕𝐹𝑋(𝑎)
𝜕𝑎 = 2√𝜆𝑅𝐷𝜆𝐵𝑅𝐾0(2√𝜆𝑅𝐷𝜆𝐵𝑅𝑎) (21)
𝑓𝑌(𝑏) =𝜕𝐹𝑋(𝑏)
𝜕𝑏 = 2√𝜆𝑆𝑅𝜆𝐵𝑆𝐾0(2√𝜆𝑆𝑅𝜆𝐵𝑆𝑏) (22)
3.1. Outage probability (OP)
The OP of system can be given as
𝑂𝑃 = 𝑃𝑟(𝛾𝑆𝑅𝐷< 𝛾𝑡ℎ) (23)
where 𝛾𝑡ℎ= 22𝑅− 1 is the threshold of system and R is source rate. Substituting (11) into (23), we have 𝑂𝑃 = 𝑃𝑟 (𝜅𝛹𝑋𝑌
𝑋+𝑌 < 𝛾𝑡ℎ) = 𝑃𝑟(𝑋[𝜅𝛹𝑌 − 𝛾𝑡ℎ] < 𝛾𝑡ℎ𝑌)
= {𝑃𝑟 (𝑋 < 𝛾𝑡ℎ𝑌
𝜅𝛹𝑌−𝛾𝑡ℎ) , 𝑌 >𝛾𝑡ℎ
𝜅𝛹
1, 𝑌 ≤𝛾𝑡ℎ
𝜅𝛹
= ∫0𝛾𝑡ℎ𝜅𝛹𝑓𝑌(𝑦)𝑑𝑦+ ∫ 𝐹𝑋 𝛾𝑡ℎ∞ 𝜅𝛹
( 𝛾𝑡ℎ𝑌
𝜅𝛹𝑌−𝛾𝑡ℎ|𝑌 = 𝑦) × 𝑓𝑌(𝑦)𝑑𝑦 (24)
Applying (19-22), (24) can be rewritten as (25).
𝑂𝑃 = ∫ 2√𝜆0∞ 𝑆𝑅𝜆𝐵𝑆𝐾0(2√𝜆𝑆𝑅𝜆𝐵𝑆𝑦)𝑑𝑦− 4 ∫
√𝜆𝑆𝑅𝜆𝐵𝑆𝜆𝑅𝐷𝜆𝐵𝑅[ 𝛾𝑡ℎ𝑦
𝜅𝛹𝑦−𝛾𝑡ℎ] ×
𝐾0(2√𝜆𝑆𝑅𝜆𝐵𝑆𝑦)𝐾1(2√𝜆𝑅𝐷𝜆𝐵𝑅[ 𝛾𝑡ℎ𝑦
𝜅𝛹𝑦−𝛾𝑡ℎ]) 𝑑𝑦
𝛾𝑡ℎ∞ 𝜅𝛹
(25)
By changing the variable for the first term of (25): 𝑡 = 2√𝜆𝑆𝑅𝜆𝐵𝑆𝑦.
𝑂𝑃 = 1
√𝜆𝑆𝑅𝜆𝐵𝑆∫ 𝑡 × 𝐾∞ 0(𝑡)𝑑𝑡
0 − 4 ∫
√𝜆𝑆𝑅𝜆𝐵𝑆𝜆𝑅𝐷𝜆𝐵𝑅[ 𝛾𝑡ℎ𝑦
𝜅𝛹𝑦−𝛾𝑡ℎ] ×
𝐾0(2√𝜆𝑆𝑅𝜆𝐵𝑆𝑦)𝐾1(2√𝜆𝑅𝐷𝜆𝐵𝑅[ 𝛾𝑡ℎ𝑦
𝜅𝛹𝑦−𝛾𝑡ℎ]) 𝑑𝑦
𝛾𝑡ℎ∞ 𝜅𝛹
(26)
Apply (6.561, 16) of the table of integral, (26) can be reformulated as
𝑂𝑃 = 1
√𝜆𝑆𝑅𝜆𝐵𝑆− 4 ∫
√𝜆𝑆𝑅𝜆𝐵𝑆𝜆𝑅𝐷𝜆𝐵𝑅[ 𝛾𝑡ℎ𝑦
𝜅𝛹𝑦−𝛾𝑡ℎ] ×
𝐾0(2√𝜆𝑆𝑅𝜆𝐵𝑆𝑦)𝐾1(2√𝜆𝑅𝐷𝜆𝐵𝑅[ 𝛾𝑡ℎ𝑦 ]) 𝑑𝑦
𝛾𝑡ℎ∞ 𝜅𝛹
(27)
3.2. Intercept probability (IP) The IP can be defined by
𝐼𝑃 = 𝑃𝑟(𝛾𝐸≥ 𝛾𝑡ℎ) (28)
substituting (14) into (28) and then applying formulas in (19) or (20), finally we have:
𝐼𝑃 = 𝑃𝑟(𝜅𝛹𝑍 ≥ 𝛾𝑡ℎ) = 1 − 𝑃𝑟 (𝑍 <𝛾𝑡ℎ
𝜅𝛹) = 2√𝜆𝐵𝑅𝜆𝑅𝐸𝛾𝑡ℎ
𝜅𝛹 × 𝐾1(2√𝜆𝐵𝑅𝜆𝑅𝐸𝛾𝑡ℎ
𝜅𝛹 ) (29)
4. NUMERICAL RESULTS AND DISCUSSION
The influence of η on the OP and IP is plotted in Figure 3 and Figure 4 for various values of ψ. Here we set α = 0.5, R = 0.5 bps/Hz and ψ = 1, 5, 10 dB. The first observation one can see from these results is that the analytical match very well with the simulation results. Figure 5 and Figure 6 illustrated the optimal switching time system OP and IP versus ψ for η = 0.8, R=0.5 bps/Hz, and α = 0.25, 0.5, 0.85 respectively.
It should be pointed out that the simulation and analytical results are the same.
Figure 3. IP versus η
Figure 4. OP versus η
Figure 5. IP versus ψ
Figure 6. OP versus ψ
5. CONCLUSION
In this research, we proposed and investigated physical security with power beacon assisted in half- duplex relaying networks over a Rayleigh fading channel. In this model, the source (S) node communicates with the destination (D) node via the helping of the intermediate relay (R) node. The D and R nodes harvest energy from the power beacon (PB) node in the presence of a passive Eavesdropper (E) node. Then we derived the integral form of the system outage probability (OP) and closed form of the intercept probability (IP). The correctness of the analytical of the OP and IP is verified by the Monte Carlo simulation.
The influence of the main system parameters on the OP and IP also is investigated. The research results indicated that the analytical results are the same as the simulation ones.
ACKNOWLEDGMENTS
This research was supported by National Key Laboratory of Digital Control and System Engineering (DCSELAB), HCMUT, VNU-HCM, Vietnam.
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